After drilling a hole through a subsurface formation and determining that the formation can yield an economically sufficient amount of oil or gas a crew completes the well. Once completed, a variety of events may occur to the formation causing the well and its equipment to require a “work-over.” For purposes of this application, “work-over” and “service” operations are used in their very broadest sense to refer to all activities performed on or for a well to repair or rehabilitate the well, and also includes activities to shut in or cap the well. Generally, workover operations include such things as replacing worn or damaged parts (e.g., a pump, sucker rods, tubing, and packer glands), applying secondary or tertiary recovery techniques, such as chemical or hot oil treatments, cementing the wellbore, and logging the wellbore, to name just a few.
During drilling, completion, and well servicing, personnel routinely insert into and/or extract equipment such as tubing, tubes, pipes, rods, hollow cylinders, casing, conduit, collars, and duct from the well. For example, a service crew may use a workover or service rig (collectively hereinafter “service rig” or “rig”) that is adapted to, among other things, pull the well tubing or rods and also to run the tubing or rods back into the well. Typically, these mobile service rigs are motor vehicle-based and have an extendible, jack-up derrick complete with draw works and block. The crew may inspect the extracted tubing and evaluate whether one or more sections of that tubing should be replaced due to physical wear, thinning of the tubing wall, chemical attack, pitting, or other defects. The crew typically replaces sections that exhibit an unacceptable level of wear and note other sections that are beginning to show wear and may need replacement at a subsequent service call.
During rod or tubing removal, a rig operator typically lifts a stand of tubing (or rods) which is then held in place by slips (or elevators for rods) while the stand is separated from the remaining portion of the tubing or rod string in the well. Once the stand of tubing has been separated from that which is still in the well, the stand of tubing can be placed on a tubing board. During conventional lifting operations, the rig operator has a full range of control of the speed at which the tubing or rods are lifted out of the well. With this, operators have a tendency to want to remove the rods, tubing or other equipment out of the well as quickly as possible in order to complete the job in a timely manner. However, by removing equipment from the well at a speed that is too high, the opportunities for damaging the well, the equipment, and the workers around the well dramatically increases.
In addition, as the stands of tubing (or rods) are being pulled out of the well, the total amount of weight on the string is reduced and the length of the string is reduced. When there are only a few stands of tubing left in the well, pulling the tubing out at a typical rate of speed, can become more dangerous because, if the tubing snags or drags in the well, there is less overall elasticity within the remaining length of tubing, and therefore, less time to react to problems caused by the hang-up in the well. This too can cause dangerous conditions around the wellhead.
Furthermore, during logging operations or when the equipment, such as tubing, is being inspected within the well the inspection data can be misleading if the logging equipment or the tubing (when the logging equipment is stationary) is being pulled too quickly, thereby limiting the usefulness of the inspection data.
Therefore, there is a need in the art for a system and method for monitoring the block speed for a rig during a pulling or running operation and limiting the maximum allowable speed of the block, thereby limiting the speed of the equipment that is attached to the hook of the rig. Furthermore, what is needed is a method and apparatus for evaluating the task being completed by a rig and the hookload and/or rig load to determine if the speed of the block should be limited to a maximum allowable speed. Furthermore what is needed in the art is a method for evaluating the task being completed by a rig and the amount of equipment remaining in the well to determine if the speed of the block should be limited to a maximum allowable speed. In addition, what is needed in the art is a system and method for disabling the lock-up system for a transmission driving the block when the hookload is light or only a small portion of the equipment, such as tubing, remains in the well during a pulling operation.
The present invention is directed to solving these as well as other similar issues in the well service area.